Brain Structures Flashcards
Forebrain =
Telencephalon (Cerebrum = 2x Cerebral Hemispheres) + Diencephalon (Thalamus, Hypo-/Subthalamus)
Cerebral Hemispheres = covering of
gray matter + white matter + deep structures (basal ganglion, limbic struct)
Separating cerebral hemispheres =
Longitudinal Fissures
Separating temporal lobe from parietal/frontal lobes =
Lateral / Sylvian Fissures
Separating occipital lobe from parietal lobe (seen only in medial surface) =
Parietooccipital Fissures
Frontal Lobe: separated from parietal lobe by
central sulcus
Pre-Central Gyrus:
area directly anterior to central sulcus = contains 1° motor areas
Frontal Lobe Lateral + Medial Surfaces:
initiate AND regulate voluntary motor activity
Frontal Lobe (Left) Lateral Surface:
contains Broca Motor Speech Area (motor aspect of language)
Frontal Lobe Medial Surface:
emotional aspects of behavior = Cingulate Gyrus
Frontal Lobe Prefontal Association Areas:
remainder of frontal lobe; emotion, motivation, personality, social inhibition
Parietal Lobe:
associated with somatosensory function = self-perception / spatial orientation
Post-Central Gyrus:
area directly posterior to central sulcus = contains 1° somatosensory area
Parietal Lobe Lateral + Medial Surface:
cortical processing of pain, touch and limb position
Parietal Lobe (Left) Lateral Surface:
sensory aspects of language in Wernicke Area
Occipital Lobe:
associated with visual information
Occipital Lobe Calacrine Sulcus:
located on medial surface; on either side of sulcus are 1° Visual Areas
Occipital Lobe Visual Association Areas:
surround 1° visual areas; mediate seeing and recognition
Temporal Lobe:
associated with auditory information
Superior Temporal Gyrus:
ability to hear and process what is heard
Temporal Lobe Lateral Surface:
perception of language
Temporal Lobe Anterior/Medial Surfaces:
learning, memory and emotion
Limbic Lobe:
not true lobe; ring of cortex covering frontal, temporal and parietal lobes
Forms Cingulate and Parahippocampal Gyri = overlies limbic system structures
Basal Ganglia: Definition/Function
interconnected nuclei contributed by forebrain, diencephalon and midbrain
Function to initiate and control voluntary movement; smooths out motor movements of limbs and axial muscles
Forebrain: Basal Ganglia:
deep in cerebral hemispheres = caudate nucleus and stratium (plutamen + globus pallidus) nuclei
Diencephalon: Basal Ganglia:
contributes subthalamic nuclei
Midbrain: Basal Ganglia:
contributes substantia nigra
Limbic Structures: associated with
drive, emotion, learning, memory
Deep forebrain contributions are amygdala (tip of tail caudate nuclei) + hippocampus (both located in temporal lobe)
Association Fibers:
within same hemisphere
Commissural Fibers:
to similar area in other hemisphere; largest = corpus callosum
Projection Fibers:
in/out of cortex; largest = coronoa radiata bundled into internal capsule
Diencephalon:
paired structures around 3rd Ventricle
Includes: Thalamus, Hypothalamus, & Subthalamus
Thalamus:
gatekeeper for the cortex; processes sensory (except olfactory) > motor info on way to cortex
Hypothalamus
integrates endocrine, autonomic function
Subthalamus:
contains subthalamic nuclei contribution to basal ganglion; important in movement/muscle tone
Brainstem =
conduit (ascending/descending paths) + integrative via reticular formation nuclei in midline + CNs
Midbrain Organization
Most rostral areas ~ sup/mid/inf cerebral peduncles (anterior) + sup/inf colliculi (posteriorly)
Peduncles = extensions of internal capsule; corticospinal (spinal cord) + corticobulbar (brainstem) tracts
Colliculi = superior = visual reflexes; inferior = auditory reflexes
Midbrain Important Structures:
cerebral aqueduct (connect 3rd + 4th ventricles) + red nucleus / substantia nigra (deep)
Hindbrain ~
Pons + Medulla
Pons
- Anterior surface =
basal pons = bundles of longitudinal corticospinal fibers + transverse pontocerebellar fibers
Pons
- Transverse pontine nuclei =
transfer information from transverse pontocerebellar fibers to opp cerebellum via middle cerebellar peduncle
Pons
- Posterior surface =
4th ventricle and superior cerebellar peduncle
Medulla:
most caudal component; fuses with spinal cord
Medulla:
- Anterior surface
mainly pyramids containing descending corticospinal fibers
Medulla:
- Lateral surface
mainly olives overling olivary nuclear complex (modulates motor activity)
Medulla:
- Posterior surface
mainly caudal 4th ventricle
Medulla:
- Posterio-lateral
surface mainly inferior cerebellar peduncle
Medulla:
- Caudal most portion =
4th ventricle narrows —> central canal of spinal cord
Caudal Medulla
has decussation of pyramids (crossing) anteriorly and fasiculus gracilis + cuneatus (sensory) post
Cerebellum =
outgrowth of pons overlying 4th ventricle
Cerebellum
Organization:
two hemispheres with central vermis and cortex covering surface
Attached to brainstem via cerebellar peduncles (recall surface of pons)
Carry information to/from cerebellum via peduncles
Ventricular System ~
Fluid-Filled Brain Space
Lateral Ventricles:
associated with the four structural lobes of the cerebrum near caudate nucleus
Third Ventricle:
via ventricular foramen of Monro; think diencephalon structures (thalamus)
Fourth Ventricle:
communicates w/3rd ventricle via the cerebral aqueduct or aqueduct of Sylvius. Cerebral aqueduct (perfectly midline) is surrounded by midbrain; 4th ventricle by brainstem.
CSF Functions:
↓ weight (suspend), “lymph” function, intra-thecal injections, neuroTx (widespread fx)
CSF Circulation ~
Lateral –> 3rd –> 4th –> Subarachnoid Space + Central Canal of Spinal Cord –> Reabsorption
4th –> Subarachnoid:
via lateral foramina of Luschka and medial foramen of Magendie
4th –> Central Canal:
direct narrowing of 4th ventricle
CSF Circulation Pattern:
posterior around spinal cord (10% reabs) —> back to subarachnoid space anteriorly —> 90% reabsorbed
CSF Reabsorption:
via arachnoid granulations from subarachnoid space into superior sagittal venous sinus
Arachnoid granulations =
1-way valve that allow flow into venous sinus but not back; also have tight junctions
Hydrocephalus ~
Water Head ~ ↑CSF in Brain
Hydrocephalus Non-Obstructive:
damage/blockage to arachnoid granulations / 1-way valve (meningitis) —> ↓absorption —> ↑CSF
Hydrocephalus Obstructive:
obstruction prevents normal circulation (tumor/developmental issue) —> ↑ ventricle size
Hydrocephalus Treatment:
surgical shunt from ventricle —> peritoneal cavity (CSF can be absorbed)
Choroid Plexus Structure:
outpouching of capillaries and pia mater into ventricular space
Choroid Plexus - Triple Lining:
capillary, pia, and choroid epithelium (ventricle epithelium lining plexus)
- Ventricular epi not lining plexus = Ependymal Cells with Gaps
- Note choroid cells have tight junctions (prevent toxic substances from blood)
CSF Production:
capillary —> active tx thru choroid epi —> passive H2O (osmolarity)
Blood Brain Barrier (BBB) Structure:
systemic caps have fenestration; brain cap has tight junction
In addition, neuropil side of capillary provides astrocyte foot processes lining cap
If asked “What is BBB?” answer
“Tight Junctions btw Capillary Endothelium”
Circumventricular Organs: monitor
blood chemistry
Circumventricular Organs: areas LACK a
BBB so they can sample the blood chemistry & alter brain function / protective brain mechanisms
Circumventricular Organs:
- Location:
- Examples:
line the ventricular system (∴ “Circumventricular”) organ vasculosum (monitor electrolyte balance) and neurohypophysis (posterior pituitary, concern hormone function)
Dura Mater
- Separation of
- Innervation:
- Blood:
periosteal/meningeal layer = sinuses
ant/mid = CN V; post = CN X (Meningeal)
middle meningeal artery (epidural hematoma)
Arachnoid Mater
- Attach to
- Subarachnoid space =
- Subdural space
pia via arachnoid trabeculae (collagen)
cerebral arteries/veins
if bleed btw subarachnoid/dura mater
Pia Mater
- Follows
- Vessels penetrating
- they get a sleeve of pia =
gyri and sulci
neuropil from subarachnoid space
perivascular space
the joining of meningeal layers of dura mater —>
thick membranes such as falx cerebri, tentorium cerebelli, diaphragma sella, falx cerebelli
True (Non-Pathologic, Exists Normally) Epidural Space in Spinal Cord
Recall that dura mater has no periosteal layer in the spinal cord; ∴ true epidural space exists containing fatty tissue and venous plexus
Continuation of Meningeal Layers in Peripheral Nerves ~
dura & arachnoid mater continue (not PIA); form epineurium (dura) & perineurium (arachnoid)
Extradural Hematoma
(Btw Bone + Osteal Dura Mater)
- Outside trauma –> mid meningeal artery
Subdural Hematoma
(“Shaken Baby Syndrome”)
- Shake ruptures bridging veins btw sinus/cerebral vein
Subarachnoid Hematoma
- Seen with arterial aneurysm (“Worst headache ever!”)
Internal Carotid Artery (ICA)
Course
Enters skull via carotid foramen —> bony canal (no lacerum) —> carotid canal —> cavernous sinus —> hairpin turn
- At hairpin, gives off first branch = Opthalmic Artery
- Post hairpin, joins Circle of Willis (CoW)
Internal Carotid Artery (ICA) Provides Majority of
Anterior Arterial Circulation
Vertebral Artery
Course
subclavian -> C6 to C1 Transverse Foramen —> Foramen Magnum —> Basilar Artery (medulla/pons junction)
Circle of Willis (CoW) ICA System (recall prior to CoW gives of opthalmic a at hairpin)
- Receive posterior communicating aa as continuing on as middle cerebral arteries
- Proximally gives off medial / lateral lenticulostriate aa
- Gives off anterior cerebral arteries which are connected by A1 Segment & Anterior Communicating aa
- A1 segment refers to part of anterior cerebral artery proximal to anterior communicating a; A2 is distal
Circle of Willis (CoW)
Vertebrobasilar System
- Vertebral a ascend —> give off posterior inferior cerebellar aa —> form basilar a & give off anterior inferior cerebellar aa, pontine aa & superior cerebellar aa
- Terminate into posterior cerebral aa which connect to ICA via posterior communicating arteries
Veins
- Superior Sagittal Sinus + Straight Sinus —> Confluence of Sinus —> Transverse —>
Sigmoid —> IJV
Recall straight sinus =
inferior sagittal sinus + Great Cerebral Vein of Galen
Recall superior petrosal sinus —>
transverse sinus BUT inferior petrosal sinus —> sigmoid / IJV
